Molybdenum-columbium alloys



Patented May 11, 1954 UNITED) STATES. PATENT OFF-ICE MOLYBDENUMsCOLUMBIUM ALLOYS John' L. Ham; Dearborn, Frederick P. Bcns andv Alvin J. Herzig,- Detroit, and George A. Tim-' mons wFerndale, Mich., assignors to Climax- MolybdenumCompany, New York, N. Y., a corporationrof Delaware- No Drawing. ---Application October 6, 1951,

SerialiNo. 250,207

13 Claims..

The present invention relates to alloysof mo-. lybdenum and columbium whichare capable of being worked at elevated. temperatures by forging, pressing, rolling extrusion, and other. Similar."

lar' methods. Thisinvention is also -concerned with molybdenum-columbiumalloys containing minor quantities, of otherelements'and to such alloys. in which a part of the molybdenum has.

been replaced by tungsten.T 7, Such alloys are useful in general, in applications which ,,-require highzstrength and hardness at ,elevated. temperatures and more specifically in such applia cations-r as electrodes forheating molten glass, die-casting dies for brass and other metals-etc. This application is a continuation-in-part of Applicants .copending. application,-- Serial No.-

218,523,,filed March 30, 1951,..now abandoned.

It is one of the objects of the-presentinvena tion to provide improved molybdenum-base ale.

loys which are capable of beingworked'atelevated temperatures. T

A further objectof this invention. is to provide molybdenum base, alloys; which. are superior to molybdenumin strength and..hardness both at room and elevated temperatures.

A still, further object-of the. invention is to provide-molybdenum-base alloys which retain. at elevated temperatures,. hardening inducedby working at elevated temperatures, and .in which the carbidephaselis dispersed :by the addition of the alloying element.

A further object is to. providecast.molybdenumbase alloyshaving the .aboveadvantages. -r

The terms -cast and castingi a's usedsin this specification areintended to desigmLtethelproduct resulting from the melting of metaland solidi-.

fying. the same in a mold, whether .or notlthe metal has been subjectedto subsequentworke ing or machinin The .t.erm...-casting.,.is also...

used to designate any process or method which involves meltingmetal. and. solidifying the same in amold,

In accordance with; this;,invention, 'molybdenum alloys having the above-mentioned properties are produced when columbium is used as an alloying element. -While suchalloys maybe produced by pressing and sintering-metal powders; the preferred -alloysof the present inven tion are produced by casting-since-it' has not been iound practical to produce pieces of large cross section by pressing and 'sintering'. Cast alloys, of

molybdenum and columbium are capable'oi being.

worked'at elevated temperatures only when the alloy contains limitedamOunts-of oxygen-and It has previously been established that the pres ence of minute amounts of oxygen in a casting of molybdenum or a molybdenum-base alloy seriously impairs or destroys the capacityoi the casting to be worked at elevated temperatures if the 7 oxygen is segregated at the'grain boundariesin the form of certain metallic oxides; The detrimental oxide is visible on microscopicexamination of intergranular fractures and'is believed to consist largely of M002. However, the oxidesof certain other metals, if present; are also detri In any event, when examined micro-- mental. scopically, castings which can be worked at ele-' vated temperatures have no visible oxide segregations at the grain boundaries: which are similar to the manifestations of M002. Cast "molybdenum containing less than about .001% oxygen can we worked at elevated temperatures but it is very difficult in the productiontof cast ingots of molybdenum and its alloys to reduce the oxygen content of the 'metal to such a low value.

As set forth in Frederick P. Benset al.;- Patent No. 2,580,273, the'detrimental'oxide segregationi is not found in molybdenum castingscontaining not more than .005% oxygen if small amountszof L carbon are present. Such castings can be worked at elevated temperatures.

It is nowfound that the detrimental oxide's'may Y also be eliminated by incorporatingin the-casting certain metals which'have a stronger affinity for. oxygen than does molybdenum and form f oxides which either do not segregate at the grain boundaries or, if segregated at the boundaries; T provide greater intergranular cohesion than does the oxide of molybdenum.- Aluminum and beryllium have been found to .fulfill these requirements, and forgeable castings of molybdenum and molybdenum-base alloys containingup to amaxi:

mum. of .05% oxygen have been produced by incorporating small: quantities of aaluminum -or beryllium or both in thecasting. Carbon mayv alsobe present-,if desired, and'small quantities?: of carbon or aluminumare particularlybeneficial.. in molybdenum-base alloys containing -beryl-;--

lium.

The effect of oxygen .on the molybdenumbination. This critical effect of oxygen on the capacity of the alloy to be worked at elevated temperatures is peculiar to cast alloys as distinguished from those produced by sintering metal powders.

If carbon is present in amounts between 01% and 04% and no aluminum or beryllium is present, the maximum oxygen content which can be tolerated in a casting that must be worked at elevated temperatures is about 005%. The minimum quantity of residual carbon should, preferably, increase within these limits the residual oxygen content approaches .005 Larger amounts of carbon up to a maximum of about 25% may be present in a casting that must be worked at elevated temperatures, but the resulting additional carbides increase the diiliculty or" working the cast alloy without imparting other advantages and, therefore, it is preferred that the carbon not exceed about 07%.

If aluminum or beryllium is present in adequate quantites, the maximum oxygen content which can be tolerated in a casting that must be worked at elevated temperatures is about 05%. The quantity of aluminum or beryllium must be at least suflicient to stoichiometrically react with the oxygen present in the final alloy to form AlzOs or BeO, and is preferably three times that quantity in the case of aluminum, Thus, aluminum in the range of 003% to 4% or beryllium in the range of 001% to 03% may be present. In actual practice, aluminum is prefe ed to beryl-- lium for this purpose and, if beryllium is used, it is preferred to use small quantities of aluminum or carbon with the beryllium. When aluminum is present within the range stated, residual carbon is preferably omitted altogether or es not exceed .02%. However, cast molybdenuin columbium alloys containing aluminum and as high as 06% carbon can be worked at elevated temperatures. When beryllium is used, it is preferred that th carbon not exceed 36%.

Excellent results are achieved in the working of molydenum-columbium castings containing carbon in the range of 02% to 05% and oxygen less than 003%; or aluminum from 003% to 2% and oxygen less than 112%; or beryllium from .G01% to 132%- and oxygen less than 02%. Quantities of aluminum and beryllium above the minimum required to react with the oxygen have other beneficial effects and hence aluminum may be present up to a maximum or" about 2.5% or beryllium up to a maximum of about .25 Ho; ever, as set forth hereinafter, the amount of columbium present must be reduced below its maximum ii" the aluminum exceeds about .l% or the beryllium exceeds about 03% and the alloy is to be worked at elevated temperatures.

Molybdenum-base alloys containing aluminum,

or berryllium and the herein disclosed process for producing such alloys are more fully disclosed and claimed in applicants copending applications, Serial No. 250,202, on Molybdenum-Tungsten-Aluminum Alloys, and Serial No. 250,201, on Cast Alloys and Method for Heat-Treating the Same, both filed concurrently herewith.

When molybdenum is alloyed with columbium, the columbium addition increases the hardness and strength both at room and elevated temperatures. Columbium is also efiective in dispersing the carbide phase away from the grain boundaries and in imparting a pronounced tendency to retain work-hardening at elevated temperatures. Columbium as an alloying constituent is also advantageous in that the alloy lends itself readily to melting in vacuum. Cast molybdenum-base alloys containing up to about 10% columbium can be worked at elevated temperatures to a beneficial degree. Particularly beneficial alloys are obtained when the columbium content is kept between 1% and 5%, and this range is preferred. The addition or" .25% columbium is effective in improving the high temperature properties of the alloy, but percentages of columbium below .25% have not been found to be particularly advantageous. Alloys of from 25% to 10% columbium in molybdenum are solid solutions at room temperature.

If desired, tungsten may be present in an amount not exceeding the molybdenum present. The substitution of tungsten for molybdenum has the effect of increasing the hardness of the alloy but to a lesser degree than that caused by the addition of columbium. If the maximum percentage of tungsten is employed in a cast molybdenum-base alloy containing the maximum percentage of columbium, the resulting alloy cannot be successfully worked at elevated temperatures. However, cast alloys containing tungsten which are capable of being worked at elevated temperatures are obtained if the columbium percentage is proportionately decreased toward the minimum of .25% as the tungsten percentage is increased toward its maximum of about 50%. It is to be understood that the relationship between the tungsten and columbium contents relates only to the maximum allowable columbium which may be present for a given tungsten percentage without interfering with working, and that alloys containing less columbium and tungsten than the maximums fall within the scope of this invention. Actually, it is preferred to use no tungsten or amounts less than 10%. Working of molybdenum-columbium castings is facilitated if the oxygen content is decreased toward the practical minimumof about 001% as the amounts of columbium or tungsten increase.

The useful effects of columbium in molybdenum-base alloys are realized as long as, in a given alloy, molybdenum is present in an amount exceeding the amount of tungsten present, if any, and the total of the molybdenum and tungsten contents constitutes at least of the alloy. Minor quantities of other elements may also be present. Thus, certain hereinafter listed transition elements produce advantageous effects when added to the molybdenum-columbium alloys of the present invention. However, to produce a cast alloy which can be worked at elevated temperatures to a beneficial degree, the amounts of tungsten, other transition elements, aluminum and beryllium must be limited; the preferred alloys contain at least molybdenum. Thus, even in pure binary alloys of molybdenum, the following beneficial transition elements should not be present in amounts exceeding the following percentages if the alloy is to be worked at elevated temperatures.

Beryllium in amounts in excess of 03% and up to a maximum of about 25% and aluminum in amounts in excess of .4=%and up to a'maximum of 2.5% have an efiect on workability similar to that of the above transition elements. They all produce a proportionate increase in hardness at 1600 F. as their quantities increase toward the above maximums. The maximum amounts given above for beryllium, aluminum and each of the transition elements other than tungsten correspond roughly to those quantities of each element which, when added alone to molybdenum, will produce a hardness at 1600 F. of 200 V. P. N. (Vickers pyramid numeral) in an annealed casting. It has not been possible with normal working techniques to achieve a worthwhile percentage of recovery from the working of metals and alloys having greater hot-hardness, but a beneficial working at temperatures substantial- 1y above 1600 F'., may be performed on the alloys of the present invention provided the hardness at 1600 F. does not exceed about 200 V. P. N. in an annealed casting. The effects of all of the above-mentioned metals, also columbium and tungsten, on hot-hardness are additive and, therefore, when two are present the maximum permissible amount of one should be proportionately reduced from its maximum given to the extent that the other approaches its maximum if the alloy is to be capable of being worked at elevated temperatures to a beneficial degree. Still further reductions on the same basis must be made if more than two are present, and in all cases less than those maximums gives the best results. From the standpoint of high strength and hardness at elevated temperatures in a molybdenum-columbium alloy that is well adapted to working, the preferred alloying transition elements are titanium, zirconium, tantalum and vanadium.

Molybdenum-base alloys characterized primarily by the beneficial eifects of zirconium, titanium, tantalum and vanadium, respectively, are more fully disclosed and claimed in applicants copending applications, filed concurrently herewith, as follows: Serial No. 250,206, Molybdenum-Zirconium Alloys; Serial No. 250,204, Molybdenum-Titanium Alloys; Serial .No. 250,205, Molybdenum-Tantalum Alloys; Se rial No. 250,203, Molybdenum-Vanadium Alloys.

It has been noted that additions of .01% to 5% thorium to cast molybdenum or tungsten increase the temperature to which the worked metals maybe heated without excessive grain coarsening and without becoming embrittled. Thus, thorium within the range-stated may be present in the alloys of this invention.

Therefore, the expression balance consisting essentially of molybdenum occurring in the following claims, means that the alloys called for are those whose primary characteristics result I from the presence of columbium in molybdenum, but that the alloys may also contain quantities of unspecified elements, such as the above-mentioned transition elements, which do not appreciably impair the beneficial efiects of columbium or destroy the capacity ofthe alloy to be worked at elevatedtemperatures to a beneficial degree.

The following exemplary compositions may be successfully cast, worked at elevated'temperatures, and have useful properties:

Example Columbium 2.54%. Carbon' .075

Oxygen Less than .005%. Molybdenum Balance.

Example 2 Columbium 5.81%. Carbon 075%. Oxygen Less than .005%. Molybdenum Balance.

1 .Example 3 Columbium 9.2%. Carbon .059%. Oxygen Less than .005%. Molybdenum Balance.

' Example 4 Columbium 5%. Tungsten 5%. Carbon .02%. Oxygen Less than .003 Molybdenum Balance.

EmampZe 5 Columbium 4.1%. Aluminum 25%. Oxygen 018%. Molybdenum Balance.

Example 6 Columbium. 6.3%. Carbon .01%. Beryllium .01%. Oxygen .025%. Molybdenum Balance.

The alloys of this invention may be made by a variety of procedures, but cast alloys containing carbon are preferably made by the process which consists in the steps of (1) mixing molybclenum, columbium, carbon and any other desired elements in the form of powders, in the desired proportions; (2) pressing the mixture into successive pellets to form a continuous rod; (3) sintering the rod to impart sufficient strength to the same to render it self-supporting; and (4) arc-melting the sintered-rod as a consumable electrode in a vacuum and collecting the metal directly into a water-cooled copper mold.

The starting materials used in the process are commercially'pure molybdenum powder, preferably containing not more than about 05 oxygen, and commercially available carbon and coir-unbium powders; as well as the powders of any other elements employed; Metals in the form oi small chips or granules comprise a part of the charge. lhe starting materials are analyzed for carbcn and oxygen, and the amount of carbon required to stoichiemetrically react with the oxygen present to form. carbon monoxide and to provide a residual carbon-content of at least 01% but less than 25% is emplcyed.

I The powder charge is-fedinto an extrusion die positioned beneath the ram oia reciprocating press wherein: successive pellets of powder material are pressed continuously on top of preeeding pellets to form a continuous rod of pressed metal powders. Pelleting pressures of approximately 10,000 p. ski. to1120,000 p. s. i. have been used, witlil lBOG p. s. i. normally being adequate. The pressing is accomplished in a vacuum-tight container.

Suflicient strength tomake the pressedmetal rod self-supporting isimpartedby sintering the rod in vacuum at'a temperature' of approximately 2400? F. to 2900" F. for approximately a-qua'rter of a minute to severalminutes. Sintering may be accomplished by any well-known method of heating; electrical resistance heating is preferred.

The sintered rod is then used as a consumable electrode in a vacuum arc furnace. Melting is started by striking an are between the rod and a starting electrode comprising a pile of chips of the same or similar alloy placed on a disc of molybdenum at the bottom of the casting mold. A water-cooled copper mold has been found suitable for receiving the molten molybdenum columbium alloy without contaminating the alloy with copper. Molten alloy striking the watercooled copper mold quickly solidifies, forming a protective coating on the surface of the mold. Thereafter, the liquid alloy becomes the lower electrode and the upper, consumable electrode is mechanicallyfed toward the lower, liquid electrode to maintain. continuous melting with the proper arc spacing.

For steps 2, 3 and 4, the pressure within the container should be as low as possible and should not exceed a maximum of 500 microns, and preferably should be below 100 microns. All three of these steps may be carried out in the same container.

If aluminum or beryllium or any other relatively volatile element is employed in the alloy, the above-described process cannot be practiced under the degree of vacuum set forth above and hence it is necessary to employ an inert atmosphere of higher pressure in the melting chamber, An argon or helium atmosphere at or slightly above atmospheric pressure has been found suitable for this purpose. Except for the change from vacuum to an inert atmosphere at higher pressure, the process previously described may be used. The desired quantities of aluminum or beryllium are added to the mixture of metal powders which are sintered to produce the consumable electrode.

Inasmuch as extremely minute quantities of oxygen impair the capacity or" the alloy cast to be hot-worked, the starting materials should be as low in oxygen as possible and it is necessary to avoid the introduction of significant amounts of oxygen as a contaminant in the inert atmosphere. The inert atmosphere may be purified by circulating it through a commercial drying tower before introduction into the casting container. The gas may be recirculated or re-used after passing over a bed of titanium metal maintained at approximately 1500" and a bed of magnesium metal maintained at approximately 1l00 F. Because of the relatively high volatility of aluminum at the are temperature, the pressure of the inert atmosphere within the container is preferably maintained at substantially atmospheric pressure or slightly above, for example, up to about 15.5 pounds per square inch. The casting container is first evacuated and then flushed with the inert gas; and, during operation, the inert gas is bled into the casting container to maintain atmospheric pressure or slightly above.

If carbon is employed in addition to aluminum or beryllium, the partial pressure or carbon monoxide in the melting chamber should be maintained below about 100 microns. In some cases, this may require a flow of purified inert gas through the chamber.

One suitable form of apparatus for use in forming, sintering and melting the powder rod is disclosed in the copending application of Edgar K. Leavenworth, Serial No. 787,797, filed Novem- 8 ber 24, 1947, now Patent No. 2,651,952, issued September 15, 1953.

Microscopic examination of a large number of molybdenum-columbium alloys indicated that the addition of columbium redistributes the carbide phase, leaving little carbide segregation at the grain boundaries. The substantial absence of carbide at the grain boundaries beneficially contributes to the ability of the alloy to be worked at elevated temperatures and increases its plasticity.

Results from a large number of tests of molybdenum-columbium alloys having compositions within the aforementioned limits indicated that these alloys are outstanding in their capacity to retain at elevated temperatures, hardening induced by working. The testing procedure and typical results are set forth below. The alloy of Example 2 in the form of a bar 1 /2 inches in diameter and 2%; inches long having a hardness of 231 V. P. N. in the annealed casting was heated at 2100 F. and extruded in a die having a diameter of .55 inch. After extrusion, the hardness was 350 V. P. N. The as-extruded bar was then annealed for 1 hour at 2400 F. and the hardness was unaltered. After annealing 1 hour at 2600" F., it was reduced only to 272 V. P. N. An unalloyed molybdenum sample containing a comparable amount of carbon when subjected to the same treatment loses 50% of the work-hardening induced by extrusion after 1 hour at 130W and 100% after 1 hour at 2000 F.

All of the proportions given herein proportions by weight in the final alloy.

What is claimed is:

l. A cast alloy consisting of at least 85% molybdenum and characterized by its capacity to be worked at elevated temperatures and its cacity to retain a significant amount of work hardness after one hour at 2200 said alloy containing from 25% to 10% coluznbium from .003% to 4% aluminum, from zero to carbon, oxygen less than 02%, and the balance consisting essentially of molybdenum.

2. A cast alloy consisting of at least 85% molybdenum and characterized by its capacity to be worked at elevated temperatures and its capacity to retain a significant amount of work iardness after one hour at 2209" B, said alloy containing from .25 to 10% columbium; at least one element from the group consisting of carbon from .0l% to 25%, aluminum from 1.303% to 2.5% and beryllium from .0Ol% to .2575; metal from the group consisting of the transition elements titanium from zero to 14%, vanadium from zero to 7%, chromium from zero to 2%, iron from zero to 1.3%, cobalt from zero to .9 nickel from zero to 4%, zirconium from zero to 2%, tantalum from zero to 9%, and tungsten from zero to 10%, the total amount of metal from said group of transition elements being further limited to an amount. within the range from none to the amount which will increase the hardness of the annealed casting to a value not exseeding 200 V. P. N. at 1600 R; and the balance consisting essentially of molybdenum.

3. A cast alloy consisting of at least 35 molybdenum and characterized by its capacity to be worked at elevated temperatures and its capacity to retain a significant amount of work hardness after one hour at 2280" E2, said alloy containing from 25% to 10% columbium; from .003% to .4% aluminum; from zero to .02% carbon; oxygen less than 02%; metal from the group consisting of the. transition elements titanium from zero to 14%, vanadium from zero to -'7%,

1.3%, cobalt from zero to 59 %-,nickel from--zero to .4%, zirconium from zero to 2%';*-tantalum from zero to9%,: and tungsten from zero to the total amount of metal from. said group of transition"elementsbein'gffiirther"limited" to an "essentially of molybdenum.

4. A cast alloy consisting of at least 85% molybdenum and characterized by its capacity to be Worked at elevated temperatures, said alloy containing from 25% to 10 columbium; at least one element from the group consisting of carbon from .0l% to 25%, aluminum from 003% to 2.5% and beryllium from 001% to 25%; metal from the group consisting of the transition elements titanium from zero to 14%, vanadium from zero to 7%, chromium from zero to 2%, iron from zero to 1.3%, cobalt from zero to .9%, nickel from zero to .4%, zirconium from zero to 2%, tantalum from zero to 9%, and tungsten from zero to 10%, the total amount of metal from said group of transition elements being further limited to an amount within the range from none to the amount which will increase the hardness of the annealed casting to a value not exceeding 200 V. P. N. at 1600 F.; and the balance consisting of molybdenum.

5. A cast alloy characterized by its capacity to be worked at elevated temperatures and its capacity to retain a significant amount of work hardness after one hour at 2200 F., said alloy casting comprising from 25% to 10% coiumbium, carbon from 01% to 25%, oxygen not more than 005%, and the balance consisting essentially of molybdenum.

6. A cast alloy characterized by its capacity to be worked at elevated temperatures and its capacity to retain a significant amount of work hardness after one hour at 2200 F., said alloy casting comprising from 25% to 10% columbium, oxygen not more than .05%, aluminum in an amount at least sufiicient to react with all of the oxygen present and not more than 2.5%, the maximum amount of aluminum within the range stated being reduced toward 4% as the amount of columbium approaches its upper limit, and the balance consisting essentially of molybdenum.

7. A cast alloy characterized by its capacity to be worked elevated temperatures and its capacity to retain a significant amount of work hardness after one hour at 2200 F., said alloy casting comprising from 25% to 10% columbium, oxygen not more than .05%, beryllium in an amount at least sufficient to react with all of the oxygen present and not more than 25%, the maximum amount of beryllium within the range stated being reduced toward .03% as the amount of columbium approaches its upper limit, and the balance consisting essentially of molybdenum.

8. A cast alloy consisting of at least 85% molybdenum and characterized by its capacity to be worked at elevated temperatures, said alloy casting containing from 25 to 10% columbium, carbon from .01 to 25%, oxygen not more than .005%,'metal from the group consisting of the transition elements titanium from zero to 14%, vanadium from zero to 7%, chromium from zero to 2%, iron from zero to 1.3%, cobalt from zero to .9 nickel from zero to .4%, zirconium from zero to 2%,tantalum from-zero to 9%, and tungsten from zero to 10 thetotal amount of metal from said group of transition elements being further limited to an amount within the range from none to the amount which 'will increase the hardness of the annealed casting to a value not exceeding 200 V. P'. N. at1600" F., and thebalance consisting of molybdenum.

9. A cast alloy consisting of at least 85% molybdenum and characterized by its capacity to be "worked at elevatediemperatures, said alloy casting'comprising"from;25% to 10% 'c'olumbium,

oxygen not more than .05%, aluminum in an amount at least sufficient to react with all of the oxygen present and not more than 2.5%, the maximum amount of aluminum within the range stated being reduced toward 04% as the amount of columbium approaches its upper limit, metal from the group consisting of the transition elements titanium from zero to 14%, vanadium from zero to 7%, chromium from zero to 2%,. iron from zero to 1.3%, cobalt from zero to .9%, nickel from zero to .4%, zirconium from zero to 2%, tantalum from zero to 9%, and tungsten from zero to 10%, the total amount of metal from said group of transition elements being further limited to an amount within the range from none to the amount which will increase the hardness of the annealed casting to a value not exceeding 200 V. P. N. at 1600 F., and the balance consisting of molybdenum.

10. A cast alloy consisting of at least 85%.

molybdenum and characterized by its capacity to be Worked at elevated temperatures, said alloy casting comprising from 25% to 10% columbium, oxygen not more than .05%, beryllium in an amount at least sufiicient to react with all or the oxygen present and not more than 25%, the maximum amount of beryllium within the range stated being reduced toward 03% as the amount of columbium approaches its upper limit, metal from the group consisting of the transition elements titanium from zero to 14% vanadium from zero to 7%, chromium from zero to 2%, iron from zero to 1.3%, cobalt from zero to .9%,. nickel from zero to .4%, zirconium from zero to 2%, tantalum from zero to 9%, and tungsten from zero to 10%, the total amount of metal from said group of transition elements being further limited to an amount within the range from none to the amount which will increase the hardness of the annealed casting to a value not exceeding 200 V. P. N. at 1600 F., and the balance consisting of molybdenum.

11. A cast, molybdenum-base alloy characterized by its capacity to be worked at elevated ternperatures, said alloy casting comprising from 25% to 10% columbium, carbon from .O1% to 07%, oxygen not more than 003%, and the balance consisting of molybdenum.

12. A cast, molybdenum-base alloy characterized by its capacity to be worked at elevated temperatures, said alloy casting comprising from 25% to 10% columbium, aluminum from 503% to .4%, carbon not more than .06%, oxygen not more than .05%, the minimum amount of aluminum within the range stated being that required to combine with all of the oxygen in the alloy to form aluminum oxide, and the balance consisting of molybdenum.

13. A cast, molybdenum-base alloy characterized by itscapacity to be worked at elevated temperatures, said alloy casting comprising from 25% to 10% columbium, beryllium from 001% to .03%, carbon not more than 06%, oxygen not 11 more than 05%, the minimum amount of beryllium within the range stated being that required to combine with all of the oxygen in the alloy to form beryllium oxide, and the balance consisting of molybdenum.

References Cited in the file of this' patent UNITED STATES PATENTS Number Name Date 969,064 Kuzel Aug. 10, 1910 1,363,162 Myers et a1 Dec. 21, 1920 12 Number Name Date 1,385,072 Arenagli July 19, 1921 2,188,405 Hensel et a1. Jan. 30, 1940 2,304,297 Anton Dec. 8, 1942 Parke et al.: Treatise in Transactions of American Institute for Mining and Metallurgical Engineers, vol. 171, 1947, pages 416-430.

10 Kessler et a1., 1949. Preprint No. 33 of paper presented at the American Society for Metals Convention, Cleveland, Ohio, October 17-21, 1949. 

1. A CAST ALLOY CONSISTING OF AT LEAST 85% MOLYBDENUM AND CHARACTERIZED BY ITS CAPACITY TO BE WORKED AT ELEVATED TEMPERATURES AND ITS CAPACITY TO RETAIN A SIGNIFICANT AMOUNT OF WORK HARDNESS AFTER AN HOUR AT 2200* F., SAID ALLOY CONTAINING FROM .25% TO 10% COLUMBIUM FROM .003% TO .4% ALUMINUM, FROM ZERO TO .02% CARBON, OXYGEN LESS THAN .02%, AND THE BALANCE CONSISTING ESSENTIALLY OF MOLYBDENUM. 